Image forming apparatus and control method for the same

Abstract

An image forming apparatus that is capable of generating highly accurate read timing of a patch image, thereby achieving highly accurate density adjustment and improving color stability. A patch image for color adjustment is read in read timing generated when a trigger bar is detected. The patch image and the trigger bar that are to be read by a color sensor are formed on a transfer material. Image formation is executed by a printer controller in an image forming condition set differently for the trigger bar and for the patch image.

1. An image forming apparatus comprising:
 an image forming device that forms, on an image bearing member, an image with a plurality of materials, a patch image for detecting density of the image, and a trigger image to be detected to generate a trigger to read the patch image, wherein the patch image is formed with a first material among the plurality of materials and the trigger image is formed with a second material, which is different from the first material, among the plurality of materials; 
 a reading device that reads the patch image based on the trigger generated by detecting the trigger image; and 
 a controlling device that controls the density of the image formed by said image forming device based on the patch image read by said reading device, 
 wherein a brightness of the trigger image formed with the second material is lower than that of the patch image formed with the first material. 
 
     
     
       2. An image forming apparatus according to  claim 1 , wherein the plurality of materials include black, cyan, magenta, and yellow materials, and the second material that forms the trigger image is the black material. 
     
     
       3. An image forming apparatus according to  claim 1 , wherein the trigger image is further formed with at least one of the plurality of materials other than the black material in addition to the black material. 
     
     
       4. An image forming apparatus according to  claim 1 , wherein each of the first material and the second material comprises a toner. 
     
     
       5. An image forming apparatus according to  claim 1 , wherein images formed by developing electrostatic latent images are transferred to the bearing member as the patch image and the trigger image. 
     
     
       6. An image forming apparatus according to  claim 1 , wherein the bearing member is a sheet on which the image is to be recorded. 
     
     
       7. An image forming apparatus comprising:
 an image forming device that forms, on an image bearing member, an image with a plurality of materials, a patch image for detecting density of the image, and a trigger image to be detected to generate a trigger to read the patch image, wherein the patch image is formed with a first material among the plurality of materials, and the trigger image is formed with a black material, which is one of the plurality of materials; 
 a reading device that reads the patch image based on the trigger generated by detecting the trigger image; and 
 a controlling device that controls the density of the image formed by said image forming device based on the patch image read by said reading device. 
 
     
     
       8. An image forming apparatus according to  claim 7 , wherein the trigger image is further formed with at least one of the plurality of materials other than the black material in addition to the black material. 
     
     
       9. An image forming apparatus according to  claim 7 , wherein each of the plurality of materials comprises a toner. 
     
     
       10. An image forming apparatus according to  claim 7 , wherein images formed by developing electrostatic latent images are transferred to the bearing member as the patch image and the trigger image. 
     
     
       11. An image forming apparatus according to  claim 7 , wherein the bearing member is a sheet on which the image is to be recorded.